Many types of spacecraft, such as geosynchronous communication satellites, spin about a geometric axis during transfer orbit. One purpose is to take advantage of spin stability of the spacecraft while satisfying thermal and power constraints. A number of disturbance torques, which can be caused by incremental velocity or spin speed change maneuvers, for example can alter the attitude of the spacecraft. More specifically, these disturbances can induce nutation in the spacecraft. Furthermore, a mass redistribution during the transfer orbit spin can induce wobble in the spacecraft.
Known approaches to nutation damping include active nutation damping such as disclosed in U.S. Pat. No. 5,012,992 issued to Salvatore. A problem with these known nutation damping approaches is that they do not account for wobble control.
Wobble control has been done by open loop dynamic balancing which requires an estimate of the mass properties of the spacecraft, in-flight iteration, and adjustment after major maneuvers. Spacecraft typically include a large number of spin to transverse inertia ratios and the geometric wobble angle may change drastically during the transfer orbit. A problem with open loop dynamic balancing is the necessity of iterative ground procedures for controlling the wobble. The success of a mission requires a stabilized spin, effective nutation damping, and wobble control.
Thus, a need has arisen for a method and system which damps nutation while simultaneously automatically rebalancing the spacecraft (i.e., eliminating wobble) after mass property changes thereby eliminating iterative ground procedures.